1. Field of the Invention
The present invention relates generally to an inflatable medical balloon, and more particularly, to a method and mold for fabricating medical balloons. The mold has a unique configuration with a dual angle taper region to provide both a more defined and distinct taper region, and optimally thin and flexible taper and shaft dimensions.
2. Background of the Invention
Inflatable medical balloons associated with balloon catheters are well known in the art, and are commonly used in, for example, percutaneous transluminal coronary angioplasty (PTCA) or delivery of a vascular stent or stent graft. During a PTCA procedure, a balloon catheter is used to dilate arteries obstructed by plaque in order to improve blood flow through the artery. Stents are used as prosthetic devices to support weakened or diseased vascular walls to avoid catastrophic rupture thereof. In either procedure, the balloon catheter is normally advanced through the patient's arterial system until the obstruction is reached. The balloon catheter must typically follow a narrow and tortuous path in order to reach the desired destination. Because of the difficulty of proceeding along such a pathway during a PTCA procedure or stent delivery, the balloon is advanced through the patient's arterial system in a deflated configuration, generally folded around the catheter to as low a profile as possible.
Medical balloons used for these procedures typically include a cylindrical main body/working length, shafts that attach the balloon to the catheter, and tapered transition regions that join the shafts to the main body. Ideally, the main body and the shafts would be connected perpendicularly, which would permit for a folded configuration with a very low profile. However, manufacturing limitations currently require the use of tapered transition regions, as the perpendicular transition region is extremely difficult to mold.
The process of fabricating such balloons using mold technologies is well known in the art. One example of a manufacturing process employing a mold is as follows. The process generally begins by placing an extruded cylindrical tubular parison made of a drawable polymer having a specified diameter and wall thickness into the cavity of a mold. The parison is then heated to a blowing temperature. While in this amorphous state, the parison is pressurized so that it will expand and the parison material will be forced against the inner molding surfaces of the mold cavity. Simultaneously with this expansion, the parison is also drawn longitudinally. The completed balloon is then removed from the mold.
Unfortunately, blowing medical balloons using mold technology is somewhat limited in its ability to form a clear and distinct taper region and working length transition that can be used to measure the working length of the balloon accurately. As a particular patient's arterial system and obstructions will reflect a specific geometry the physician performing the procedure will choose a balloon according to the dimensions of that balloon. Therefore, the physician must be able to know with precision the dimensions of the balloon.
Increasing the angle of the taper relative to the longitudinal axis of the mold can help make the working length more defined and distinct. However, the increased angle can make forming the shaft and taper sections of the balloon more difficult. The result can be undesirable artifacts in the balloon material, such as stretch marks and thickness anomalies, as well as suboptimal taper and shaft dimensions. For example, the dimensions of the taper and the shaft may be too thick, which would make the taper and the shaft less flexible and less capable of being folded to a low profile on the catheter.